Oxygen Diffusion Coefficient in Isolated Chicken Red and White Skeletal Muscle Fibers in Ontogenesis

Abstract

Oxygen diffusion from medium to cultured isolated muscle fibers from red gastrocnemius muscle (deep part) (RGM) and white pectoralis muscle (WPM) of embryonic and postnatal chickens (about 6 months) was explored. The intracellular effective O2 diffusion coefficient (Di) in muscle fiber was calculated from a model of a cylindrical fiber with a uniform distribution of an oxygen sink based on these experimentally measured parameters: critical tension of O2 (PO2) on the surface of a fiber, specific rate of O2 consumption by a weight unit of muscle fibers (VO2), and average diameter of muscle fibers. The results document the rapid hypertrophic growth of RGM fibers when compared to WPM fibers in the second half of the embryonic period and the higher values of VO2 and critical PO2 during the ontogenetic period under study. The oxygen Di in RGM fibers of embryos and 1-day chickens was two to three times higher than observed for WPM fibers. For senior chickens, the oxygen Di value in RGM and WPM fibers does not differ. The Di of O2 in both RGM and WPM fibers increased from 1.4–2.7 × 10−8 to 90–95 × 10−8 cm2/s with an ontogenetic increase in fiber diameter from 7.5 to 67.0 μm. At all stages the oxygen Di values in RGM and WPM fibers are significantly lower than the O2 diffusion coefficient in water: for 11-day embryos they are 889 and 1714 times lower and for adult individuals 25 and 27 times lower, respectively. Why oxygen Di values in RGM and WPM fibers are so low and why they are gradually increasing during the course of hypertrophic ontogenetic growth are still unclear.